(a) Field of the Invention
The present invention a method and an apparatus of signal detection, and more particularly, to a method and an apparatus of signal detection using a log likelihood ratio in a multi-input multi-output wireless communication system.
(b) Description of the Related Art
In a wireless communication system, since a bandwidth is very limitative, it is very important to support a high data transmission rate to various users by using only the limitative bandwidth. A multiple-input multiple-output (hereinafter, referred to as “MIMO”) communication system has several antennas on a transmitter and a receiver and simultaneously transmits multiple signals by using the same wireless band on the transmitter in order to meet the above-mentioned requirement. As a result, it is possible to remarkably improve transmission rate without increasing the bandwidth.
In the MIMO communication system, the transmitter transmits different data by using a plurality of antennas, and in this case, a signal of each antenna experiences independent fading. Therefore, the receiver should differentiate transmitted data through proper signal processing. At this time, signals transmitted from another antenna are overlapped and thus cause inter-antenna interference which is an interference factor increasing errors.
As a method of detecting the transmitted data while removing the Interference factors, a maximum likelihood (hereinafter, referred to as “ML”) method is used. This method shows the best performance, but is very high in complexity of a signal detecting process. In particular, as the number of transmission antennas increases, the complexity increases exponentially. Therefore, a modified ML (hereinafter, referred to as “M-ML”) method having low complexity while providing the same performance as the ML method is proposed.
However, in the MIMO system, since signals transmitted by a single-input multiple-output (SIMO) scheme and signals transmitted by a multiple user-MIMO (MU-MIMO) scheme are used, a case in which using the ML method is optimal and a case in which using the M-ML method is optimal at the time of detecting the signal are mixed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.